The present invention generally relates to picture producing apparatuses, and more particularly to a picture producing apparatus for storing picture data within a picture information which is transmitted in a picture memory and for outputting an analog video signal which is obtained from the picture data read out from the picture memory.
Conventionally, a personal computer is used as a picture producing apparatus. The personal computer decodes commands entered via a keyboard and writes picture data in a video random access memory (hereinafter simply referred to as a V-RAM). Data stored in a color look up table (hereinafter simply referred to as a CLUT) are re-written according to the needs. Primary color signals for displaying a picture are produced from the picture data which are successively read out from the V-RAM. In such a personal computer, the decoding of the commands, the write-in to the V-RAM, the re-wirting of the data in the CLUT and the like are performed by a single central processing unit (CPU). The CPU processes a command only after processing a previous command. Thus, when a certain command is entered while executing a command, the CPU waits until the execution of the command is completed before executing the certain command.
However, sub-codes reproduced from a compact disc on a compact disc player are successively supplied to the picture producing apparatus, and the CPU must de-interleave the sub-codes, detect errors and correct the errors. The conventional picture producing apparatus performs the processing such as the de-interleaving of the sub-codes, the detection of the errors, the correction of the errors, decoding of the commands, the write-in to the V-RAM, the re-writing of the data in the CLUT and the like by use of the single CPU. For this reason, in the case where the incoming commands require clearing of the picture, a scroll-with-present for coloring with a different color an empty portion which is formed by moving the picture and the like, there is a problem in that the CPU cannot process the commands in real time. In addition, in order to reduce the burden on the CPU, a large portion of the write-in process to the V-RAM is performed by hardware, that is, by a device often referred to as a graphic display processor. However, the graphic display processor is originally designed to mainly control the read-out of the picture data from the V-RAM, and for this reason, there is a problem in that the construction thereof becomes complex when the graphic display processor is to perform the additional function of controlling the write-in to the V-RAM.